Insulating ring and protective device for cathode-ray tubes



July 1, 1952 R. A. FISCH 2,602,114

INSULATING RING AND PROTECTIVE DEVICE FOR CATHODE-RAY TUBES Filed April10, 1950 INVENTOR 33 Flaw/mo A fisc ATTORNEYS Patented July 1, 1952 iUNITED; STATES PATENT OFFICE.

' L'INSULATING RIN G AND. PROTECTIVE DEVICE FOR, CATHODE-RAY'TUB'ESRichard A. Fisch, Kew Gardens, N. Y;

Application April 10', 1950, Serial No. 154,938

This invention relate to novel" device for shielding and protecting ametal backed television or cathode ray "tube, more particularly itrelates to a novelmeans for attaching an insulating shield to such atube and for retaininga protective plate of glass in front-of theviewing end of saidtube. I I v I This application is acontinuation-in-part of applications Serial No. 73,058, filed January27, 1949 (issued as- Patent No. 2,593,813 dated April 1i, 1959)andSerial No. 104,289, filed July 12;, 1949.

The general idea of shielding electrical equip ment having exposedpartsis old and well known but the shielding of metal backed cathode rayor television tubes presents peculiar difiicul-ties. The metalhackedcathode ray or television tubes comprise a glass bulbcontainingthe electrode structure, a metal tube section which has a varyingdiameter (usually frustoconical) the small end of which is united to theend of the glass bulb and a glass lens element which is united to theopen e r-large end of the said metal tube. In order that a good sealcan'b'e obtained between the lens and the-metal backing, the metal backor conical section is flaredoutwardly at the'large end-to form av seatfor the round edge portion-of the lens. It is desirableto have ashieldwhich fits closely about the metal backing-and it is essential toprovide insulating means-Which fits over the flared portion ofthe'tubesin'ce the flared rim: adjacent thelens is the part which'ismostlikely to be contacted when the setis mounted in a cabinet. i

An object. of this invention therefore is to provide an improvedinsulatingiguard or shield for a metal backedcathode ray tube togetherwith a means for holding the shield in'place about the tube.

Another object of the invention is to provide an improved insulatingring for the flarfidh tim portion of a metalbacked cathode ray ortelevision tube provided with means ior holding .a. protective lens infront. of the sealed lersoi the,

cathoder-ay tube.

Another objectof the invention is to provide anovel'm'eans for secuus'an insulating shield to cathode ray or television tube. which alsocooperates to securely mount the tube, to the chassis of the set. jAnother object of the invention is to provide anew ring ofinsulatingniaterial adapted to hold a shield in place oniatelevisiontube, adaptedgto' aid in mounting the tube on the chassis and alsoadapted to hold a protective lens in front-of' the lens of thetelevision tube; r 1

a claims. (01. 177-318)..

Another object oi-theinvention is to provide a method and means forsecuring a conically shaped shield to a television tube and forattaching the combined shield and tube to a cabinet;

It is a further object of this invention to provide a combination of atelevision or cathode ray tube, an insulating and mounting ring and aprotective glass plate.

These objectsv and others ancillary thereto are obtainedbymaking' aclamping ring'member fromfflexi ble insulating material adapted to fitsnugly about-the fiared portion of the tube. Preferably the clampingring member has the cross sectional shape of a distorted H having,however, threelegs on the inside thereof; two of the three of the legsof the H fit about or straddle the flange and the third leg cooperateswith the center leg to hold the protective plate of glass which istobe-fl xed in front of the lens. The two outside. legs of the H extendaway from the flanged edgeforming a. groove therebetween adapted to holda suitable elastic securing member which in turn holds the clampingmember tightly about the flanged edge of the tube. The outside groove ofthe clamping member which holds the elastic member also is made. deepenough to hold a heavy elastic cord the ends of which. are secured tothe body of the chassis so that said elastic cordis adapted to hold theend of the tube in position on the saidchassis. v

The ring must fit snugly about the flared end of "the tubeand thereforemust be open at one area to permit the inside groove to straddle theflared flange-oi the'tube. It is difiicult to make the ring with suchprecision that it fits together at-the-cut portion after being insertedon the considerably; Since the metal back is under such a high voltagethat any small almost insignificant opening or break in the insulatingring is enough to permit a spark or static charge to seek a ground andseverely shockany person or animal who approaches too close to theuninsulated area. Small pieces ofinsulating material may be placedinside oi the opening in the ring but this expedi ent does not have theapproval of the Underwriters Laboratories because such pieces are easilylost or misplaced when atelevision set is being repaired and there is noassurance that they would be replaced. The ring made according to thisinvention has an integral flap on one end of the open ringadapted to fitunder the other end of the ringso that ever-y'portion oi the flange ofthe television tube must always be covered by insulating material.

In some cases a. plate glass is placed in front of a television tube toprevent injury if the tube should explode. Since the lens of the tubealso collects an electrical charge, this lens will ordinarily collectdust and it is difficult to clean the dust from between the plate glassand the lens. In application No. 73,058, filed January 27, 1949, I havealready proposed to provide a clove tail groove in one of the outeredges of the clamping member and into the dove tail groove I insert anelastic projecting ring or gasket which seals oif the space between thering and the plate glass. According to the present invention the plateglass protecting member is held by the clamping member. The plate glassmember may be coated at the edges to form a mask to cut out portions ofthe picture on the television tube lens.

In general any resinous plastic material which has insulating propertiesmay be employed to make the insulating devices of the present invention.The hydrocarbon polymeric materials such as polyethylene,polyisobutylene, polystyrene, polymers and copolymers of butadienes,polymers and copolymers of methyl substituted homologues of butadienesuch a isoprene, etc. are very suitable as the material for theinsulating devices. Other polymeric materials having high insulatingvalues which may be employed are the polymers and copolymers ofvinylidenechloride and vinyl fluoride, polyvinyl carbazole, polyvinylnaphthaline, etc. Impregnated fabrics such as cellulose acetateimpregnated with vinyl butyral and similar materials may also beemployed.

The clamping member may be formed by an extrusion process, by aninjection molding process or by any other-molding process. When formedby extrusion it is necessary to mold the thin flap portion after theextruded strip is formed and cut to shape. Th clamping member is shownas circular in outline but it can have any desired outline depending onthe peripheral shape of the cathode ray tube. For example, it may beelliptical, rectangular or polygonal in outline.

It has been learned that the said skirt portion of the insulating deviceis not' necessarybutit is adesirable protective device from the point ofview of servicemen or users of cathode ray tubes not connected withtelevision such as in laboratories andthe like.

The novel features characteristic of this invention are set forth withparticularity inthe appended claims. The invention itself, however, bothas to its organization and its method of operating, together withadditional objects and advantages thereof, will best be understood fromthe following description of specific embodiments when read inconnection with the accompanying drawings in which: 7

Figure 1 is a top plan view of a symmetrical half of a televisiontubewith the shield and clamp of the present invention attached thereto.

Figure 2 is a cross-section detail view showing how the clamping memberholds the protective plate glass and the protective shield in place withrespect to the television tube.

Figure 3 is a rear plan view of the clamping ring made according to theinvention.

Figure 4 is a rear View of the clamping-ring, cathode ray tube, andmounting meansshowing how the ring may be employed to secure the cathoderay tube to the chassis of a television set.

Figure 5 is a detail view partly broken away of the separated ends ofthe ring. 1 j

The television tube for which this invention is specially useful isshown in Figure 1 and comprises the s-ocket ID, the glass bulb sectionII containing the electrode, the protective skirt or shield 20, theclamping ring 30 and a securing means 50. In Figure 1 the clamping ring30 is shown in the closed portion.

In order to hold the wide end of the skirt or shield at the flared endl5 of the television tube, a specially constructed clamping member 30 isprovided. This member 30 is made of stiff flexible plastic material suchas polythylene. This clamping member has the general outline of a circlethe size of which is about the same as that of the flange or flared endof the television tube, and the clamping member has three interior orinwardly extending annular flanges 44, 3!, and

' 32, one of which (3|) is slightly wider than the other and is adaptedto press against the back of the flange or flared end l5 of the tube.Flange (32) is adapted to extend over the edge portion of the lens I 4in the front of the tube. The clamping member also includes two exterioror outwardly extending annular flanges 33 and 35 with a groove orchannel 34 formed therebetween. The annular flanges (3|, 32, and 44especially) are made of sufficient thickness and extend at such an anglethat they must be forced apart when the clamping member 30 is pressedtightly against the flanged or flared rim [5 of the tube so that whenthe clamping member 30 is held in place about said flared end I5 theannular flanges 3| and 32 are held tightly against and actually take theform of the flanged portion [5 of the tube as shown in the drawings. Theclamping member 30 is held in place by any desired means such as anannular securing member or band (50) which is adaptedto fit into thegroove 34.

In order to make sure that the ring 30 covers every exposed area of theflared flange portion l 5 of the tube one of the ends 60 is providedwith an integral extension SI of reduced thickness adapted to fit underthe arms 3|, 32 of the opposite end 62 as shown in Figures 3, 4 and 5.

This end portion 6| may beintegrally formed on the end 60 in any desiredway. For example the ring 30 may be cut with overlapping ends Siland 62and then the top portion of the overlapping part of the end 60 can beshaved or cut off to fit under the arms 3|, 32 of the end 62. Also, aseparate piece BI may be heat sealed to the inside portion of the end60. Or the end 6| may be molded from an excess end portion of the end 60as illustrated in Figures 3 and 5.

A preferred method of making the ring of Figure 3 is to injection moldthe whole structure in one operation.

An important feature of the instant invention is embodied in thecombination of the channel 45 formed by flanges 44 and 32 and its usewith the remaining features of the invention. If desired the channel 45can be lined with a pad 46 of felt or any other suitable material. toprevent wear at the inner corners of channel 45. Since it has been founddesirable to include a plate of glass 41 in front of the television tubeto help keep dust off the tube, to protect the tube and to act asinsulator bemn any metallic or human body which may come too close tothe charged portion of the tube,

which extends beyond lens [4 at [6, the channel 45 is provided to holdsaid plate glass 41 firmly in place. The plate glass 41 also acts toprotect fool proof ring means for securing an insulating skirt to ametal backed television or cathode ray tube which ring completely coversthe flange at the lens end of said tube and simultaneously holds aprotective glass plate firmly in place.

I claim:

1. An improved device for the mounting onto the chassis of a televisionset of a metal backed cathode-ray tube, of the type which has an annularmetal flange surrounding the metal back adjacent the lens holding endthereof, said device comprising an open annular strip of flexibleinsulating material, said strip comprising a body portion of such sizeand shape to fit closely about the annular flange of said cathode raytube, three continuous interior flanges extending inwardly from saidbody portion forming two channels therebetween, the first and second ofsaid interior flanges being adapted to straddle the metal flange of saidcathode ray tube and thereby insulate the flanged area of the metalbacked cathode-ray tube, the second and third of said interior flangesbeing adapted to hold a glass protective plate in front of the lens ofthe said cathode ray tube, a pair of substantially continuous exteriorflanges extending from said body portion of said strip, said exteriorflanges forming a channel opposite the channel formed by the first andsecond interior flanges, the said channel formed by said exteriorflanges being adapted to hold a first retaining member for flxing theopen annular strip upon said cathode ray tube and also being adapted tohold a second retaining member for fixing the strip and tube combinationto a chassis, the opening in said annular strip forming two abuttingends, an integral channel-like extension on one of said abutting endsadapted to fit within the interior channel formed by the first andsecond interior flanges at the opposite abutting end to assure thecomplete insulation of said flanged area of the cathode ray tube.

2. A device for mounting on the chassis of a television receiver a metalbacked cathode-ray tube, of the type which has an annular metal flangesurrounding the metal back adjacent the lens holding end thereof, saiddevice comprising an open annular strip of flexible insulating material,said strip comprising a body portion of such size and shape to fitclosely about the annular flanges of said cathode ray tube, threecontinuous interior flanges extending inwardly from said body portionforming two channels therebetween, the first and second of said interiorflanges straddling the metal flange of said cathode ray tube and therebyinsulating the flanged area of the metal backed cathode-ray tube, thesecond and third of said interior flanges holding a glass protectiveplate in front of the lens of the said cathode-ray tube, a pair ofsubstantially continuous exterior flanges extending from said bodyportion of said strip, said exterior flanges forming a channel oppositethe channel formed by the first and second interior flanges, the openingin said annular strip being formed by two abutting ends, an integralchannel-like extension on one of said abutting ends fitting within theinterior channel formed by the first and second interior flanges at theopposite abutting end to assure the complete insulation of said flangedarea of the cathoderay tube.

3. A structure for mounting a cathode-ray tube of the type having aprojecting metal flange adjacent the lens thereof, and for supporting aprotective transparent plate in front of the lens of the tube, saidstructure including an open gasket made of plastic insulating material,and tensioning means for said gasket, said gasket having a body portionwith three continuous flanges extending inwardly therefrom, the firstand second of said interior flanges forming a channel of such shape toflt about the metal flange of the cathode-ray tube, the second and thirdof said interior flanges forming a channel of such shape to flt aboutthe edge of the protective transparent plate, said gasket beingexpansible for receiving the metal flange of the tube and the protectiveplate in said channels formed therein, said gasket having two abuttingends with an integral channel-like extension on one of the abutting endsand an interior channel formed in the other abutting end for receivingsaid channel-like extension, said body portion of said gasket having apair of substantially continuous flanges extending outwardly therefromforming an exterior channel thereabout, said tensioning means includinga belt extending in said exterior channel for holding said gaskettightly against the metal flange of the tube and the protective plate,with said channel-like extension in said interior channel so that saidvgasket completely surrounds said metal flange and insulates the same.

RICHARD A. FISCH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,293,529 Bedford Aug. 18, 19422,388,203 Zindel Oct. 30, 1945 2,458,368 Kamin et a1. "Jan. 4, 19492,484,345 Hinz Oct. 11, 1949 2,497,660 Devine Feb. 14, 1950 2,503,813Fisch Apr. 11, 1950 FOREIGN PATENTS Number Country Date 520,412 GreatBritain Apr. 23, 1940 600,096 Great Britain Mar. 31. 19.48

